Polycyclohexanedimethylene terephthalate (PCT) is excellent in mechanical properties and in chemical resistance, and in addition has a higher thermal deformation temperature compared to general polyesters such as polybutylene terephthalate and polyethylene terephthalate. Therefore, there has been an expectation for PCT to be developed in applications such as electric and electronic equipment components, automobile components, and mechanical components, from which heat resistance is required.
However, the polymerization degree of PCT was easily lowered during molding, and thus the mechanical physical properties were easily lowered during molding residence in a short period of time, making it difficult to put it into practical use as a molding material. Further, PCT has low toughness and thus is fragile, so that there is a concern that a problem may occur during the use of the product.
As a means for enhancing the residence stability of PCT, there has been proposed a method of adding an epoxy compound to polyethylene terephthalate, or the like that is a similar terephthalic acid-based polyester (see PTL 1, for example). Examples of other means that have been proposed for enhancing the residence stability of PCT include a method for adding a phenol epoxy compound branched in three directions or a trifunctional allyl isocyanurate compound, a method of adding a phenoxy resin, and a method of adding a glycidyl ether ester compound (see PTL 2, for example).
As a means for improving toughness, there has been proposed a method of adding an olefin-based elastomer having an epoxy group to a polyester (see PTL 3, for example). As another means for improving toughness, there has been proposed a method of combining the above two techniques for enhancing residence stability (see PTLS 1 and 2, for example).
Further, when using a resin material for the application of electric and electronic equipment components, it is required to satisfy the flame retardancy (V-0) in accordance with flame retardancy standard (UL 94) by Underwriters Laboratories (UL) in the US, which is commonly used as an index of flame retardancy of resins. UL 94 standard includes regulations not only for the burning time of a resin during burning, but also for the drip of an ignition source; when a resin is dripped in contact with flame in vertical combustion test, it is required that a specified amount of cotton set at the lower part of a test piece should not be ignited by the drip. In addition to satisfying such high flame retardancy, it is required to have better mechanical characteristics.
Examples of methods that have been proposed for these problems include a method of adding a graft copolymer obtained by reacting an olefin-glycidyl(meth)acrylate copolymer with a (meth)acrylic ester monomer and an olefin-based resin to flame-retardant PCT (see PTL 4, for example) and a method of adding thereto a multifunctional epoxy compound and an olefin-based elastomer (see PTL 2, for example).
Furthermore, one of the preferable examples of electric and electronic equipment components for which resins such as PCT are used is a camera module. The camera module is an electronic component having a camera function, in which a lens is mounted over a CCD (charge-coupled device)/CMOS (complementary metal oxide semiconductor) imaging element (image sensor). The camera module is installed on mobile phones, laptop computers, digital cameras, digital video cameras, and the like. In a camera module having a typical fixed focus optical system, a CMOS imaging element is mounted on a signal processing chip. Furthermore, the camera module is provided with members such as one or two or more lenses for imaging an optical image on an image sensor, a barrel for holding the lenses, a holder for holding the barrel, and a substrate for holding the image sensor (see FIG. 1).
The barrel and holder need to be adaptive to reflow soldering, from the requirement for downsizing of portable electronic equipment, operations for reducing costs of mounting processes of electronic equipment, or reduction of process time. Therefore, it is necessary for a material for the barrel or holder to have heat resistance beyond 250° C. Furthermore, a material excellent in mechanical characteristics and moldability is required, and currently a liquid crystal resin composition and a semiaromatic polyamide using a long chain diamine are mainly used (see PTLS 5 to 7).